Motion analysis device, motion analysis system, motion analysis method, program, and recording medium

ABSTRACT

A motion analysis device that obtains a relation between a movement direction of a ball hitting surface of an exercise tool at a time of starting a swing and a posture of the ball hitting surface at the time of impact during the swing by using output of an inertial sensor.

BACKGROUND

1. Technical Field

The present invention relates to a motion analysis device, a motionanalysis system, a motion analysis method, a program, and a recordingmedium.

2. Related Art

In a projectile line (a course of a hit ball) of a golf ball hit by aswing of a golfer, there are types of a slice, a fade, a straight, adraw, a hook, and the like. Elements for deciding the projectile line ofa golf ball are an incident angle and a face angle of a club head at thetime of an impact (see JP-A-2011-110164 and the like). In particular, inJP-A-2011-110164, to analyze a type of projectile line, a target lineconnecting the center of a golf ball and a target is specified based ona swing video photographed by a camera and an incident angle θ and aface angle ϕ are measured using the target line as a criterion.

In the measurement method of JP-A-2011-110164, however, since the targetline is merely predicted from the video, there is a possibility of thetype of projectile line not being correctly analyzed. Further, in orderto improve analysis precision of the type of projectile line, it isnecessary to also examine a method of calculating parameters (anincident angle θ and a face angle ϕ) to be used for the analysis indetail.

SUMMARY

An advantage of some aspects of the invention is that it provides amotion analysis device, a motion analysis system, a motion analysismethod, and a program capable of acquiring effective information foranalysis or the like of a type of projectile line.

The invention can be implemented as the following forms or applicationexample.

APPLICATION EXAMPLE 1

A motion analysis device according to Application Example 1 includes afirst calculation unit that obtains a relation between a movementdirection of a ball hitting surface of an exercise tool at a time ofstarting a swing and a posture of the ball hitting surface at the timeof impact during the swing by using an output of an inertial sensor.

In the motion analysis device according to Application Example 1, it ispossible to obtain effective data for the analysis of the type ofprojectile line.

APPLICATION EXAMPLE 2

In the motion analysis device according to the application example, thefirst calculation unit may obtain, as the relation, an angle formed by avector indicating the movement direction of the ball hitting surface atthe time of starting a swing and a predetermined vector which lies alongthe ball hitting surface at the time of impact during the swing.

APPLICATION EXAMPLE 3

In the motion analysis device according to the application example, thefirst calculation unit may obtain, as the relation, an angle formed bythe vector indicating the movement direction of the ball hitting surfaceat the time of starting a swing and a predetermined vector intersectingthe ball hitting surface at the time of impact during the swing.

APPLICATION EXAMPLE 4

In the motion analysis device according to the application example, thefirst calculation unit may obtain, as the relation, an angle formed bythe vector indicating the movement direction of the ball hitting surfaceat the time of starting a swing and the predetermined vector projectedon a predetermined plane intersecting in a vertical direction.

APPLICATION EXAMPLE 5

The motion analysis device according to the application example mayfurther include a second calculation unit that obtains a relationbetween a posture of the ball hitting surface before exercise starts andthe movement direction of the ball hitting surface at the time ofstarting a swing by using the output of the inertial sensor.Accordingly, the motion analysis device according to the applicationexample can measure the posture of the ball hitting surface at the timeof impact during the swing and the movement direction of the ballhitting surface at the time of starting the swing.

APPLICATION EXAMPLE 6

The motion analysis device according to the application example mayfurther include an output processing unit that outputs data indicatingat least one of the relation obtained by the first calculation unit andthe relation obtained by the second calculation unit. Accordingly, auser can confirm at least one of his or her habit related to the postureof the ball hitting surface and his or her habit related to the movementdirection of the ball hitting surface as data on a graph.

APPLICATION EXAMPLE 7

In the motion analysis device according to the application example, theoutput processing unit may display data indicating a combination of therelation obtained by the first calculation unit and the relationobtained by the second calculation unit as a two-dimensional graph.Accordingly, the user can confirm his or her type of projectile line asdata on a two-dimensional graph.

APPLICATION EXAMPLE 8

In the motion analysis device according to the application example, theoutput processing unit may display a type of projectile line predictedfrom the data along with the graph. Accordingly, the user canobjectively recognize his or her type of projectile line.

APPLICATION EXAMPLE 9

In the motion analysis device according to the application example, theoutput processing unit may display a map in which an area is divided inaccordance with the type of projectile line along with the graph.Accordingly, the user can intuitively recognize his or her type ofprojectile line.

APPLICATION EXAMPLE 10

In the motion analysis device according to the application example, theoutput processing unit may set an origin of the graph so that an areacorresponding to a straight type of projectile line is located in amiddle of the graph. Accordingly, for example, the user can approach hisor her type of projectile line in a so-called straight manner byexercising ball hitting so that his or her data is located in the middleof the graph.

APPLICATION EXAMPLE 11

In the motion analysis device according to the application example, theoutput processing unit may display a plurality of pieces of dataregarding exercises of a plurality of times with the same graph anddistinguish recent data from the other data on the graph. Accordingly,the user can compare his or her recent type of projectile line to theprevious type of projectile line.

APPLICATION EXAMPLE 12

A motion analysis system according to Application Example 12 includesthe motion analysis device according to any one of the foregoingapplication examples; and the inertial sensor. Accordingly, in themotion analysis system according to Application Example 12, it ispossible to obtain effective data for the analysis of the type ofprojectile line.

APPLICATION EXAMPLE 13

A motion analysis method according to Application Example 13 includes:obtaining a relation between a movement direction of a ball hittingsurface of an exercise tool at a time of starting a swing and a postureof the ball hitting surface at the time of impact during the swing byusing an output of an inertial sensor. Accordingly, in the motionanalysis method according to Application Example 13, it is possible toobtain effective data for the analysis of the type of projectile line.

APPLICATION EXAMPLE 14

In the motion analysis method according to the application example, inthe obtaining of the relation, an angle formed by a vector indicatingthe movement direction of the ball hitting surface at the time ofstarting the swing and a predetermined vector which lies along the ballhitting surface at time of impact during the swing may be calculated asthe relation.

APPLICATION EXAMPLE 15

In the motion analysis method according to the application example, inthe obtaining of the relation, an angle formed by the vector indicatingthe movement direction of the ball hitting surface at the time ofstarting the swing and a predetermined vector intersecting the ballhitting surface at the time of impact during the swing may be calculatedas the relation.

APPLICATION EXAMPLE 16

In the motion analysis method according to the application example, inthe obtaining of the relation, an angle formed by the vector indicatingthe movement direction of the ball hitting surface at the time ofstarting the swing and the predetermined vector projected on apredetermined plane intersecting in a vertical direction may becalculated as the relation.

APPLICATION EXAMPLE 17

A motion analysis program according to Application Example 17 causes acomputer to perform a posture calculation procedure of obtaining arelation between a movement direction of a ball hitting surface of anexercise tool at a time of starting a swing and a posture of the ballhitting surface at the time of impact during the swing by using anoutput of an inertial sensor. Accordingly, in the motion analysisprogram according to Application Example 17, it is possible to obtaineffective data for the analysis of the type of projectile line.

APPLICATION EXAMPLE 18

A recording medium according to Application Example 18 stores a motionanalysis program that causes a computer to perform a posture calculationprocedure of obtaining a relation between a movement direction of a ballhitting surface of an exercise tool at a time of starting a swing and aposture of the ball hitting surface at the time of impact during theswing by using an output of an inertial sensor.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numbers reference like elements.

FIG. 1 is a diagram illustrating an overview of a swing analysis systemwhich is an example of a motion analysis system according to anembodiment.

FIG. 2 is a diagram illustrating examples of a mounting position anddirection of a sensor unit.

FIG. 3 is a diagram illustrating a procedure of operations performed bya user according to the embodiment.

FIG. 4 is a diagram illustrating an example of the configuration of theswing analysis system according to the embodiment.

FIG. 5 is a diagram illustrating a relation between a global coordinatesystem Σ_(xyz) and a head in an address.

FIG. 6 is a flowchart illustrating an example of a procedure of a swinganalysis process according to the embodiment.

FIG. 7 is a flowchart illustrating an example of a procedure of aprocess of detecting an impact.

FIG. 8A is a diagram illustrating a graph of triaxial angular velocitiesat the time of a swing, FIG. 8B is a diagram illustrating a graph ofcomposite values of the triaxial angular velocities, and FIG. 8C is adiagram illustrating a graph of differential values of composite valuesof the triaxial angular velocities.

FIG. 9 is a flowchart illustrating an example of a procedure of aprocess (step S60 of FIG. 6) of calculating an incident angle θ and arelative face angle ϕ′.

FIG. 10 is a diagram illustrating a face vector in an address.

FIG. 11 is a diagram illustrating a movement direction vector and a facevector at the time of starting a swing.

FIG. 12 is a diagram illustrating the incident angle θ.

FIG. 13 is a diagram illustrating the relative face angle ϕ′.

FIG. 14 is a diagram illustrating an example of a process of displayingθ and ϕ′.

FIG. 15 is a diagram illustrating a display example of a projectile lineprediction map in a background of a graph.

FIG. 16 is a diagram illustrating a difference in a type of projectileline.

FIG. 17 is a diagram illustrating an example of a histogram of therelative face angle ϕ′.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, preferred embodiments of the invention will be described indetail with reference to the drawings. The embodiments to be describedbelow do not inappropriately limit the content of the inventiondescribed in the appended claims. All of the constituents to bedescribed below may not be said to be essential constituent requisitesof the invention.

Hereinafter, a swing analysis system performing analysis of a golf swingwill be described as an example of a motion analysis system.

1. Swing Analysis System

1-1. Overview of Swing Analysis System

FIG. 1 is a diagram illustrating an overview of a swing analysis systemaccording to an embodiment. A swing analysis system 1 according to theembodiment is configured to include a sensor unit 10 (which is anexample of an inertial sensor) and a swing analysis device 20 (which isan example of a motion analysis device).

The sensor unit 10 can measure acceleration generated in each axisdirection of three axes and an angular velocity generated in eachrotation of the three axes and is mounted on a golf club 3 (which is anexample of an exercise tool).

In the embodiment, as illustrated in FIG. 2, the sensor unit 10 isfitted on a part of a shaft of the golf club 3 when one axis among threedetection axes (an x axis, a y axis, and a z axis), for example, the yaxis, conforms to the longitudinal direction of the shaft. Preferably,the sensor unit 10 is fitted at a position close to a grip in which ashock at the time of hitting is rarely delivered and a centrifugal forceis not applied at the time of swinging. The shaft is a portion of ahandle excluding a head of the golf club 3 and also includes the grip.

A user 2 performs a swing motion of hitting a golf ball 4 in apre-decided procedure. FIG. 3 is a diagram illustrating a procedure of amotion performed by the user 2. As illustrated in FIG. 3, the user 2first holds the golf club 3, takes a posture of address so that themajor axis of the shaft of the golf club 3 is vertical to a target line(target direction of hitting), and stops for a predetermined time ormore (for example, 1 second or more) (S1). Next, the user 2 performs aswing motion to hit the golf ball 4 (S2).

While the user 2 performs the motion to hit the golf ball 4 in theprocedure illustrated in FIG. 3, the sensor unit measures triaxialacceleration and triaxial angular velocity at a predetermined period(for example, 1 ms) and sequentially transmits measurement data to theswing analysis device 20. The sensor unit 10 may immediately transmitthe measurement data, or may store the measurement data in an internalmemory and transmit the measurement data at a predetermined timing suchas the end of a swing motion of the user 2. Communication between thesensor unit 10 and the swing analysis device 20 may be wirelesscommunication or wired communication. Alternatively, the sensor unit 10may store the measurement data in a recording medium such as a memorycard which can be detachably mounted and the swing analysis device 20may read the measurement data from the recording medium.

In the embodiment, the swing analysis device 20 calculates an index(which is an index of a movement direction at the time of starting aswing) Θ of a movement direction of the head of the golf club 3 at thetime of impact during the swing and an index Φ′ of a posture of a facesurface (ball hitting surface) at the time of impact during the swing,using the data measured by the sensor unit 10. Then, the swing analysisdevice 20 displays (outputs) the indexes Θ and Φ′ as graphs or the liketo a display unit (display). The swing analysis device 20 may be, forexample, a portable device such as a smartphone or a personal computer(PC).

1-2. Configuration of Swing Analysis System

FIG. 4 is a diagram illustrating an example of the configuration of theswing analysis system 1 (examples of the configurations of the sensorunit 10 and the swing analysis device 20) according to the embodiment.As illustrated in FIG. 4, in the embodiment, the sensor unit 10 isconfigured to include an acceleration sensor 12, an angular velocitysensor 14, a signal processing unit 16, and a communication unit 18.

The acceleration sensor 12 measures acceleration generated in each ofmutually intersecting (ideally, orthogonal) triaxial directions andoutputs digital signals (acceleration data) according to the sizes anddirections of the measured triaxial accelerations.

The angular velocity sensor 14 measures an angular velocity generated ataxis rotation of mutually intersecting (ideally, orthogonal) triaxialdirections and outputs digital signals (angular velocity data) accordingto the sizes and directions of the measured triaxial angular velocities.

The signal processing unit 16 receives the acceleration data and theangular velocity data from the acceleration sensor 12 and the angularvelocity sensor 14, appends time information, and stores theacceleration data and the angular velocity data in a storage unit (notillustrated). The signal processing unit 16 generates packet data inconformity to a communication format by appending time information tothe stored measurement data (the acceleration data and the angularvelocity data) and outputs the packet data to the communication unit 18.

The acceleration sensor 12 and the angular velocity sensor 14 areideally fitted in the sensor unit 10 so that the three axes of eachsensor match the three axes (the x axis, the y axis, and the z axis) ofthe xyz rectangular coordinate system (sensor coordinate system Σ_(xyz))defined for the sensor unit 10, but errors of the fitting anglesactually occur. Accordingly, the signal processing unit 16 performs aprocess of converting the acceleration data and the angular velocitydata into data of the xyz coordinate system (sensor coordinate systemΣ_(xyz)) using correction parameters calculated in advance according tothe errors of the fitting angles.

The signal processing unit 16 may perform a temperature correctionprocess on the acceleration sensor 12 and the angular velocity sensor14. Alternatively, a temperature correction function may be embedded inthe acceleration sensor 12 and the angular velocity sensor 14.

The acceleration sensor 12 and the angular velocity sensor 14 may outputanalog signals. In this case, the signal processing unit 16 may performA/D conversion on each of an output signal of the acceleration sensor 12and an output signal of the angular velocity sensor 14, generatemeasurement data (acceleration data and angular velocity data), andgenerate packet data for communication using the measurement data.

The communication unit 18 performs, for example, a process oftransmitting the packet data received from the signal processing unit 16to the swing analysis device 20 or a process of receiving controlcommands from the swing analysis device 20 and transmitting the controlcommands to the signal processing unit 16. The signal processing unit 16performs various processes according to the control commands.

The swing analysis device 20 is configured to include a processing unit21, a communication unit 22, an operation unit 23, a storage unit 24, adisplay unit 25, and an audio output unit 26.

The communication unit 22 performs, for example, a process of receivingthe packet data transmitted from the sensor unit 10 and transmitting thepacket data to the processing unit 21 or a process of transmitting acontrol command from the processing unit 21 to the sensor unit 10.

The operation unit 23 performs a process of acquiring operation datafrom the user 2 and transmitting the operation data to the processingunit 21. The operation unit 23 may be, for example, a touch panel typedisplay, a button, a key, or a microphone.

The storage unit 24 is configured as, for example, any of various ICmemories such as a read-only memory (ROM), a flash ROM, and a randomaccess memory (RAM) or a recording medium such as a hard disk or amemory card.

The storage unit 24 stores, for example, programs used for theprocessing unit 21 to perform various calculation processes or controlprocesses, or various program or data used for the processing unit 21 torealize application functions. In particular, in the embodiment, thestorage unit 24 stores a swing analysis program 240 which is read by theprocessing unit 21 to perform a swing analysis process. The swinganalysis program 240 may be stored in advance in a nonvolatile recordingmedium. Alternatively, the swing analysis program 240 may be receivedfrom a server via a network by the processing unit 21 and may be storedin the storage unit 24.

In the embodiment, the storage unit 24 stores club specificationinformation 242 indicating the specification of the golf club 3 andsensor-mounted position information 244. For example, the user 2operates the operation unit 23 to input a model number of the golf club3 (or selects the model number from a model number list) to be used andsets specification information regarding the input model number as theclub specification information 242 among pieces of specificationinformation for each model number (for example, information regardingthe length of a shaft, the position of the center of gravity, a lieangle, a face angle, a loft angle, and the like) stored in advance inthe storage unit 24. Alternatively, by mounting the sensor unit 10 at adecided predetermined position (for example, a distance of 20 cm fromthe grip), information regarding the predetermined position may bestored in advance as the sensor-mounted position information 244.

The storage unit 24 is used as a work area of the processing unit 21 andtemporarily stores, for example, data input from the operation unit 23and calculation results performed according to various programs by theprocessing unit 21. The storage unit 24 may store data necessarilystored for a long time among the data generated through the processes ofthe processing unit 21.

The display unit 25 displays a processing result of the processing unit21 as text, a graph, a table, animations, or another image. The displayunit 25 may be, for example, a CRT, an LCD, a touch panel type display,or a head-mounted display (HMD). The functions of the operation unit 23and the display unit 25 may be realized by one touch panel type display.

The audio output unit 26 outputs a processing result of the processingunit 21 as audio such as a voice or a buzzer sound. The audio outputunit 26 may be, for example, a speaker or a buzzer.

The processing unit 21 performs a process of transmitting a controlcommand to the sensor unit 10, various calculation processes on datareceived from the sensor unit 10 via the communication unit 22, andother various control processes according to various programs. Inparticular, in the embodiment, the processing unit 21 performs the swinganalysis program 240 to function as an impact detection unit 211, aposture calculation unit (which is an example of a first calculationunit) 214, a movement direction calculation unit (which is an example ofa second calculation unit) 215, and a display processing unit (which isan example of an output processing unit) 217.

For example, the processing unit 21 performs processes of receiving thepacket data received by the communication unit 22 from the sensor unit10, acquiring time information and measurement data from the receivedpacket data, and storing the time information and the measurement datain the storage unit 24 in association therewith.

The processing unit 21 performs, for example, a process of detecting atiming (measurement time of measurement data) of an impact in a swing ofthe user 2, using the measurement data.

The processing unit 21 performs a process of generating time-series dataindicating a change in the posture of the sensor unit 10 by applying theangular velocity data included in the measurement data to, for example,a predetermined calculation formula (the change in the posture can alsobe expressed by, for example, rotation angles (a roll angle, a pitchangle, and a yaw angle) of axial directions, quaternions, or a rotationmatrix).

The processing unit 21 performs a process of generating time-series dataindicating a change in the position of the sensor unit 10 by performing,for example, time integration on the acceleration data included in themeasurement data (the change in the position can also be expressed by,for example, a velocity in each axial direction (velocity vector)).

The processing unit 21 performs, for example, a process of generatingtime-series data indicating a change in the posture of the face surfaceof the golf club 3 based on the time-series data indicating the changein the posture of the sensor unit 10, the club specification information242, and the sensor-mounted position information 244.

The processing unit 21 performs, for example, a process of generatingtime-series data indicating a change in the position of the face surfaceof the golf club 3 based on the time-series data indicating the changein the position of the sensor unit 10, the time-series data indicatingthe change in the posture of the sensor unit 10, the club specificationinformation 242, and the sensor-mounted position information 244.

Here, the processing unit 21 according to the embodiment performs, forexample, the following processes (1) to (6) to measure the posture andthe position of the face surface at each time point using the time ofstopping of the user 2 (address measurement time t₀) as a criterion.

(1) The processing unit 21 corrects a bias by calculating an offsetamount included in the measurement data using measurement data(acceleration data and angular velocity data) at time t₀ and subtractingthe offset amount from measurement data (acceleration data and angularvelocity data) at a swing.

(2) The processing unit 21 decides an XYZ orthogonal coordinate system(global coordinate system Σ_(XYZ)) to be fixed to the ground based onthe acceleration data (that is, data indicating the direction of gravityacceleration) at time t₀, the club specification information 242, andthe sensor-mounted position information 244. For example, as illustratedin FIG. 5, the origin of the global coordinate system Σ_(XYZ) is set atthe position of the head at time t₀, the Z axis of the global coordinatesystem Σ_(XYZ) is set in the upward vertical direction (that is, anopposite direction to the direction of the gravity acceleration), andthe X axis of the global coordinate system Σ_(XYZ) is set in the samedirection as the x axis of the sensor coordinate system Σ_(xyz) at timet₀. Accordingly, in this case, the X axis of the global coordinatesystem Σ_(XYZ) can be considered to be a target line L0.

(3) The processing unit 21 decides a face vector V_(F) indicating theposture of a face surface S_(F). A method of adopting the face vectorV_(F) is arbitrary. In the embodiment, however, as illustrated in FIG.5, a unit vector (which is an example of a predetermined vectorintersecting the face surface (ball hitting surface)) oriented in the +Xaxis direction at time t₀ is used as the face vector V_(F). In thiscase, at time t₀, a Y axis component and a Z axis component of the facevector V_(F) are zero.

(4) The processing unit 21 sets the face vector V_(F) at time t₀ in theglobal coordinate system Σ_(XYZ) as an initial face vector V_(F)(t₀) andcalculates a face vector V_(F)(t) at each time in the global coordinatesystem Σ_(XYZ) based on the initial face vector V_(F)(t₀) and thetime-series data (after the correction of the bias) indicating a changein the posture of the face surface S_(F).

(5) The processing unit 21 decides face coordinates P_(F) indicating theposition of the face surface S_(F). A method of adopting the facecoordinates P_(F) is arbitrary. In the embodiment, a point located atthe origin of the global coordinate system Σ_(XYZ) at time t₀ is assumedto be the face coordinates P_(F). In this case, as illustrated in FIG.5, the X axis component, the Y axis component, and the Z axis componentof the face coordinates P_(F) at time t₀ are zero.

(6) The processing unit 21 sets the face coordinates P_(F) at time t₀ inthe global coordinate system Σ_(XYZ) as initial face coordinatesP_(F)(t₀) and calculates face coordinates P_(F)(t) at each time in theglobal coordinate system Σ_(XYZ) based on the initial face coordinatesP_(F)(t₀) and time-series data (after correction of the bias) indicatinga change in the position of the face surface S_(F).

Here, the correction of the bias of the measurement data is performed bythe processing unit 21, but may be performed by the signal processingunit 16 of the sensor unit 10. A function of correcting the bias may beembedded in the acceleration sensor 12 and the angular velocity sensor14.

The processing unit 21 performs a process of reading/writing variousprograms or various kinds of data from/on the storage unit 24. Theprocessing unit 21 also performs not only a process of storing the timeinformation and the measurement data received from the communicationunit 22 in the storage unit 24 in association therewith but also aprocess of storing various kinds of calculated information or the likein the storage unit 24.

The processing unit 21 performs a process of causing the display unit 25to display various images (images, text, signs, or the likecorresponding to motion analysis information (information such as theincident angle θ and the relative face angle ϕ′ (which are examples ofrelations between a posture and a movement direction of a face plane))generated by the processing unit 21). For example, the displayprocessing unit 217 causes the display unit 25 to display the images,texts, or the like corresponding to the motion analysis information(information such as the incident angle θ and the relative face angleϕ′) generated by the processing unit 21 after end of the swing exerciseof the user 2, automatically, or according to an input operation of theuser 2. Alternatively, a display unit may be provided in the sensor unit10, and the display processing unit 217 may transmit image data to thesensor unit 10 via the communication unit 22 and cause the display unitof the sensor unit 10 to display various images, text, or the like.

The processing unit 21 performs a process of causing the audio outputunit 26 to output various kinds of audio (including a voice and a buzzersound). For example, the processing unit 21 may read various kinds ofinformation stored in the storage unit 24 and output audio or a voicefor swing analysis to the audio output unit 26 after the end of theswing exercise of the user 2, automatically, or at the time ofperforming a predetermined input operation. Alternatively, an audiooutput unit may be provided in the sensor unit 10, and the processingunit 21 may transmit various kinds of audio data or voice data to thesensor unit 10 via the communication unit 22 and cause the audio outputunit of the sensor unit 10 to output various kinds of audio or voices.

A vibration mechanism may be provided in the swing analysis device 20 orthe sensor unit 10 and the vibration mechanism may also convert variouskinds of analysis information into vibration information and suggest thevibration information to the user 2.

1-3. Process of Swing Analysis Device

Swing Analysis Process

FIG. 6 is a flowchart illustrating an example of a procedure of theswing analysis process performed by the processing unit 21 of the swinganalysis device 20 according to the embodiment . The processing unit 21of the swing analysis device 20 (which is an example of a computer)executes the swing analysis program 240 stored in the storage unit 24 toperform the swing analysis process in the procedure of the flowchart ofFIG. 6. Hereinafter, the flowchart of FIG. 6 will be described.

First, the processing unit 21 acquires the measurement data of thesensor unit 10 (S10). In step S10, the processing unit 21 may performprocesses subsequent to step S20 in real time when the processing unit21 acquires the first measurement data in a swing (also including astopping motion) of the user 2 or may perform the processes subsequentto step S20 after the processing unit 21 acquires some or all of aseries of measurement data in the swing exercise of the user 2 from thesensor unit 10.

Next, the processing unit 21 detects a stopping motion (address motion)(the motion of step S1 of FIG. 3) of the user 2 using the measurementdata acquired from the sensor unit 10 (S20). When the processing unit 21performs the process in real time and detects the stopping motion(address motion), for example, the processing unit 21 may output apredetermined image or audio, or an LED may be provided in the sensorunit 10 and the LED may be turned on. Then, the user 2 is notified ofdetection of a stopped state, and then the user 2 may start a swingafter the user 2 confirms the notification.

Next, the processing unit 21 calculates the initial position and theinitial posture of the sensor unit 10 using the measurement data (themeasurement data in the stopping motion (address motion) of the user 2)acquired from the sensor unit 10, the club specification information242, the sensor-mounted position information 244, and the like (S30).

Next, the processing unit 21 detects each impact of the swing using themeasurement data acquired from the sensor unit 10 (S40). An example ofthe procedure of the impact detection process will be described below.

The processing unit 21 calculates the position and the posture of thesensor unit 10 in the swing in parallel to, before, or after the processof step S40 using the measurement data acquired from the sensor unit 10(S50).

Next, the processing unit 21 calculates the incident angle θ and therelative face angle ϕ′ of the face surface S_(F) at the time of animpact using the position and the posture of the sensor unit 10 at thetime of the impact, the position of the sensor unit 10 immediatelybefore or immediately after the impact, the club specificationinformation 242, the sensor-mounted position information 244, and thelike (S60). An example of a calculation procedure of the incident angleθ and the relative face angle ϕ′ will be described below.

Next, the processing unit 21 generates image data indicating theincident angle θ and the relative face angle ϕ′ calculated in step S60and causes the display unit 25 to display the image data (S70), and thenthe process ends. An example of the procedure of the display processwill be described below.

In the flowchart of FIG. 6, the sequence of the steps may beappropriately changed within a possible range.

Impact Detection Process

FIG. 7 is a flowchart illustrating an example of a procedure of theimpact detection process (the process of step S40 of FIG. 6) in a swingof the user 2. The impact detection process corresponds to an operationof the processing unit 21 serving as the impact detection unit 211.Hereinafter, the flowchart of FIG. 7 will be described.

First, the processing unit 21 performs bias correction on themeasurement data (acceleration data and angular velocity data) stored inthe storage unit 24 (S200).

Next, the processing unit 21 calculates a composite value n₀(t) of theangular velocities at each time t using the angular velocity data(angular velocity data at each time t) subjected to the bias correctionin step S200 (S210). For example, when the angular velocity data at timet is assumed to be x(t), y(t), and z(t), the composite value n₀(t) ofthe angular velocities is calculated in the following formula (1).n ₀(t)=√{square root over (x(t)² +y(t)² +z(t)²)}  (1)

Examples of triaxial angular velocity data x(t), y(t), and z(t) when theuser 2 performs a swing to hit the golf ball 4 are illustrated in FIG.8A. In FIG. 8A, the horizontal axis represents a time (msec) and thevertical axis represents the angular velocity (dps).

Next, the processing unit 21 converts the composite value n₀(t) of theangular velocities at each time t into a composite value n(t) subjectedto normalization (scale conversion) within a predetermined range (S220).For example, when max(n₀) is the maximum value of the composite value ofthe angular velocities during an acquisition period of the measurementdata, the composite value n₀(t) of the angular velocities is convertedinto the composite value n(t) normalized within a range of 0 to 100 bythe following formula (2).

$\begin{matrix}{{n(t)} = \frac{100 \times {n_{0}(t)}}{\max\left( n_{0} \right)}} & (2)\end{matrix}$

FIG. 8B is a diagram illustrating a graph of the composite value n(t)normalized from 0 to 100 according to formula (2) after the compositevalue n₀(t) of the triaxial angular velocities is calculated from thetriaxial angular velocity data x(t), y(t), and z(t) of FIG. 8A accordingto formula (1). In FIG. 8B, the horizontal axis represents a time (msec)and the vertical axis represents a composite value of angularvelocities.

Next, the processing unit 21 calculates a differential dn(t) of thecomposite value n(t) after the normalization at each time t (S230). Forexample, when Δt is a measurement period of the triaxial angularvelocity data, the differential (difference) dn(t) of the compositevalue of the angular velocity at time t is calculated in the followingformula (3).dn(t)=n(t)−n(t−Δt)  (3)

FIG. 8C is a diagram illustrating a graph obtained by calculating thedifferential dn(t) from the composite value n(t) of the triaxial angularvelocities in FIG. 8B according to formula (3). In FIG. 8C, thehorizontal axis represents a time (msec) and the vertical axisrepresents a differential value of the composite value of the triaxialangular velocities. In FIGS. 8A, and 8B, the horizontal axis is shownfrom 0 seconds to 5 seconds. In FIG. 8C, the horizontal axis is shownfrom 2 seconds to 2.8 seconds so that a change in the differential valuebefore and after the impact can be known.

Next, the processing unit 21 specifies the former time as measurementtime t₃ of the impact between a time at which the value of thedifferential dn(t) of the composite value is the maximum and a time atwhich the value of the differential dn(t) of the composite value is theminimum (S240) (see FIG. 8C). In a normal golf swing, a swing velocityis considered to be the maximum at a moment of an impact. Then, sincethe composite value of the angular velocity is considered to be changedaccording to the swing velocity, a timing at which the differentialvalue of the composite value of the angular velocity in a series ofswing motions is the maximum or the minimum (that is, a timing at whichthe differential value of the composite value of the angular velocitiesis the positive maximum value or the negative minimum value) can becaptured as the timing of the impact. Since the golf club 3 is vibrateddue to the impact, the timing at which the differential value of thecomposite value of the angular velocities is the maximum is consideredto be paired with the timing at which the differential value of thecomposite value of the angular velocities is the minimum. The formertiming between the timings is considered to be the moment of the impact.

In the flowchart of FIG. 7, the sequence of the steps can beappropriately changed within a possible range. In the flowchart of FIG.7, the processing unit 21 specifies the impact and the like using thetriaxial angular velocity data, but can also specify the impact and thelike similarly using triaxial acceleration data.

Process of Calculating θ And ϕ′

FIG. 9 is a flowchart illustrating an example of a procedure of aprocess (step S60 of FIG. 6) of calculating the incident angle θ and therelative face angle ϕ′. An operation of the processing unit 21 servingas the posture calculation unit 214 mainly corresponds to steps S320 andS340. A process of the processing unit 21 serving as the movementdirection calculation unit 215 mainly corresponds to steps S310 andS330. Hereinafter, the flowchart of FIG. 9 will be described.

As illustrated in FIG. 10, the processing unit 21 first sets the facevector V_(F) at measurement time t₀ of the address to the initial facevector V_(F)(t₀) (S300). As described above, the Y axis component of theinitial face vector V_(F)(t₀) is zero.

Next, as illustrated in FIG. 11, the processing unit 21 calculates amovement direction vector V_(d)(t₃) of the face surface S_(F) atmeasurement time t₃ of an impact (S310). The movement direction vectorV_(d)(t₃) is, for example, a unit vector oriented in the same directionas a vector in which face coordinates P_(F)(t₃) at time t₃ are astarting point and face coordinates P_(F)(t₃+Δt) at time (t₃+Δt) are anending point. The direction of the movement direction vector V_(d)(t₃)indicates an approximate tangential direction of a trajectory Q of theface coordinates P_(F) projected to the XY plane at time t₃.

As illustrated in FIG. 11, the processing unit 21 calculates the facevector V_(F)(t₃) of the face surface S_(F) at time t₃ (S320). Forexample, the face vector V_(F)(t₃) can be obtained from the initial facevector V_(F)(t₀) and posture change data of the face surface during aperiod from time (t₀+Δt) to time t₃.

As illustrated in FIG. 12, the processing unit 21 calculates, as theincident angle θ of the face surface S_(F), an angle formed by theinitial face vector V_(F)(t₀) projected to the XY plane (which is anexample of a predetermined plane) with respect to the movement directionvector V_(d)(t₃) projected to the XY plane (which is an example of thepredetermined plane). That is, the processing unit 21 calculates, as theincident angle θ of the face surface S_(F), an angle formed by theinitial face vector V_(F)(t₀) and the movement direction vectorV_(d)(t₃) on the XY plane (which is an example of the predeterminedplane) (S330). The incident angle θ is an angle of the tangential lineof the trajectory Q at time t₃ with respect to the target line L0 on theXY plane.

Here, as illustrated in FIG. 12, when a relation of the trajectory Qwith respect to the target line L0 is so-called “inside out”, theincident angle θ is positive. When the relation is so-called “insidein”, the incident angle θ is zero. When the relation is so-called“outside in”, the incident angle θ is negative. In this way, thedirection of θ is assumed to be decided. The trajectory Q illustrated inFIG. 12 is a trajectory of the right-handed golf club 3 and the state ofthe trajectory Q is shown when the relation of the trajectory Q withrespect to the target line L0 is so-called “inside out” (when θ ispositive).

As illustrated in FIG. 13, the processing unit 21 calculates, as therelative face angle ϕ′ of the face surface S_(F), an angle formed by aface vector V_(F)(t₃) projected to the XY plane (which is an example ofthe predetermined plane) with respect to the movement direction vectorV_(d)(t₃) projected to the XY plane (which is an example of thepredetermined plane). That is, the processing unit 21 calculates, as therelative face angle ϕ′ of the face surface S_(F), an angle formed by themovement direction vector V_(d)(t₃) and the face vector V_(F)(t₃) on theXY plane (which is an example of the predetermined plane) (S340). Then,the processing unit 21 ends the process. The relative face angle ϕ′indicates a posture relation between the vertical surface (squaresurface S) of the trajectory Q and the face surface S_(F) at time t₃.

Here, when the posture of the face surface S_(F) with respect to thesquare surface S is so-called “open”, the relative face angle ϕ′ ispositive. When the posture is so-called “square”, the relative faceangle ϕ′ is zero. When the posture is so-called “closed”, the relativeface angle ϕ′ is negative. In this way, a method of adopting ϕ′ isassumed to be decided. The trajectory Q illustrated in FIG. 13 is atrajectory formed by the right-handed golf club 3 and the state of thetrajectory Q is shown when the posture of the face surface SF isso-called “open” (when ϕ′ is positive).

In the flowchart of FIG. 9, a sequence of the processes can beappropriately changed within a possible range.

Process of Displaying θ and ϕ′

FIG. 14 is a diagram illustrating an example of a process of displayingthe incident angle θ and the relative face angle ϕ′. An example of thedisplay process described here corresponds to an operation of theprocessing unit 21 serving as the display processing unit 217.

The processing unit 21 displays data indicating combinations of θ and ϕ′on the display unit 25, for example, by plotting the data on atwo-dimensional graph having θ and ϕ′ axes, as illustrated in FIG. 14.In FIG. 14, plot destinations of marks M indicate the combination of θand ϕ′.

In the example of FIG. 14, marks Mi (where i=1, 2, . . . ) regarding aplurality of swings performed by the same user are plotted on the samegraph and the shape of the individual mark Mi indicates a type ofprojectile line of the swing corresponding to the mark Mi. In FIG. 14,for example, marks M2 and M5 corresponding to a so-called push, slice,or fade-based type of projectile line are expressed with a triangularmark, a mark M1 corresponding to a so-called pull, hook, or draw-basedtype of projectile line is expressed with a rectangular mark, and marksM3, M4, and M6 corresponding to a so-called straight-based type ofprojectile line are expressed with a circular mark.

Accordingly, the user 2 can confirm the type of projectile line of ani-th swing in accordance with the plot destination of the mark Mi andthe shape of the mark Mi.

In the example of FIG. 14, the recent mark M6 is displayed so that themark M6 is distinguished by a different form (for example, inversedisplay, blinking display, or different color display) from the othermarks M1 to M5.

Accordingly, the user 2 can distinguish his or her recent type ofprojectile line from the previous types of projectile lines.

Hereinafter, an example of a method in which the processing unit 21predicts the type of projectile line from the plot destination (thecombination of θ and ϕ′) of the mark Mi will be described.

First, when the plot destination (the combination of θ and ϕ′) of themark Mi enters within a predetermined area (dotted line range) locatednear the origin, the processing unit 21 predicts that the i-th type ofprojectile line is a so-called straight-based type of projectile line.

When the plot destination (the combination of θ and ϕ′) of the mark Miis deviated from the +θ side or the +ϕ′ side of the predetermined area(the dotted line range), the processing unit 21 predicts that the i-thtype of projectile line is a so-called push, slice, or fade-based typeof projectile line.

When the plot destination of the mark Mi is deviated from the −θ side orthe −ϕ′ side of the predetermined area (the dotted line range), theprocessing unit 21 predicts that the i-th type of projectile line is aso-called pull, hook, or draw-based type of projectile line.

In FIG. 14, the contour line of the predetermined area is drawn with adotted line. However, the contour line of the predetermined area may notbe displayed on an actual graph. In addition, when the contour line isdisplayed on the graph, the contour line can be used as a target of theuser targeting a so-called straight-based swing.

In FIG. 14, the type of projectile line is indicated with the shape ofthe mark Mi, but may be indicated with a color of the mark Mi or may beindicated by a combination of the color and shape of the mark Mi. As theshapes of the marks, various shapes such as a cross and an X form can beused in addition to the rectangular shape, the triangular shape, and thecircular shape.

The processing unit 21 may display, for example, a projectile lineprediction map illustrated in FIG. 15 as the background of theabove-described two-dimensional graph. The projectile line predictionmap is divided into areas, and text images or the like of the names ofthe types of projectile lines corresponding to the areas are assigned inthe areas.

For example, as illustrated in FIG. 15, the projectile line predictionmap is divided into 9 areas A1 to A9 arrayed in a matrix form of 3 rowsand 3 columns.

In the projectile line prediction map, a text image “Straight” of thetype of projectile line “straight” corresponding to the area A5 isassigned to the area A5 located in the middle near the origin.

In the projectile line prediction map, a text image “Push” of the typeof projectile line “push” corresponding to the area A4 is assigned tothe area A4 located on the +θ side of the area A5.

In the projectile line prediction map, a text image “Pull” of the typeof projectile line “pull” corresponding to the area A6 is assigned tothe area A6 located on the −θ side of the area A5.

Further, a text image “Push Slice” of the type of projectile line “pushslice” corresponding to the area A1 is assigned to the area A1 locatedon the +ϕ′ side of the area A4 of the projectile line prediction map.

Further, a text image “Slice” of the type of projectile line “slice”corresponding to the area A2 is assigned to the area A2 located on the+ϕ′ side of the area A5 of the projectile line prediction map.

Further, a text image “Fade” of the type of projectile line “fade”corresponding to the area A3 is assigned to the area A3 located on the+ϕ′ side of the area A6 of the projectile line prediction map.

Further, a text image “Draw” of the type of projectile line “draw”corresponding to the area A7 is assigned to the area A7 located on the−ϕ′ side of the area A4 of the projectile line prediction map.

Further, a text image “Hook” of the type of projectile line “hook”corresponding to the area A8 is assigned to the area A8 located on the−ϕ′ side of the area A5 of the projectile line prediction map.

Further, a text image “Pull Hook” of the type of projectile line “pullhook” corresponding to the area A9 is assigned to the area A9 located onthe −ϕ′ side of the area A6 of the projectile line prediction map.

FIG. 16 is a diagram illustrating a relation among the types ofprojectile lines. In FIG. 16, a relation when viewed from a right-handeduser is illustrated and individual projectile line curves are roughlydrawn to clarify differences between the types of projectile lines.

In FIG. 16, the type of projectile line denoted by reference numeral 61is an example of a projectile line curve belonging to the push. The typeof projectile line denoted by reference numeral 62 is an example of aprojectile line curve belonging to the fade. The type of projectile linedenoted by reference numeral 63 is an example of a projectile line curvebelonging to the slice. The type of projectile line denoted by referencenumeral 64 is an example of a projectile line curve belonging to thepush slice. The type of projectile line denoted by reference numeral 65is an example of a projectile line curve belonging to the pull. The typeof projectile line denoted by reference numeral 66 is an example of aprojectile line curve belonging to the draw. The type of projectile linedenoted by reference numeral 67 is an example of a projectile line curvebelonging to the hook. The type of projectile line denoted by referencenumeral 68 is an example of a projectile line curve belonging to thepull hook.

The processing unit 21 may cause the display unit 25 to display theexamples of the projectile line curves illustrated in FIG. 16, asnecessary.

1-4. Advantages

As described above, the processing unit 21 according to the embodimentcalculates the index Θ of the movement direction of the face surface atthe time of starting a swing and the index ϕ′ of the posture of the facesurface at the time of impact during the swing in order to predict thetype of projectile line of the user.

Of the indexes, the index θ of the movement direction is calculatedusing the target line as a criterion and the index ϕ′ of the posture iscalculated using the movement direction of the face surface as acriterion. Therefore, a habit of the user related to the movementdirection does not overlap on the index ϕ′ of the posture.

Accordingly, the indexes ϕ′ and θ calculated in the embodiment areconsidered as mutually independent amounts.

Accordingly, in the embodiment, the user can accurately comprehend hisor her tendency of the projectile line based on the indexes ϕ′ and θ.The processing unit 21 according to the embodiment can predict the typeof projectile line of the user based on the indexes ϕ′ and θ with highprecision.

Since the processing unit 21 according to the embodiment displays thecombination of the indexes ϕ′ and θ as the two-dimensional graph or thelike, the user can recognize his or her type of projectile line ascoordinates of the graph.

Since the processing unit 21 according to the embodiment displays theprojectile line prediction map as the background of the two-dimensionalgraph, the user can intuitively recognize his or her type of projectileline.

2. MODIFICATION EXAMPLES

The invention is not limited to the embodiments, but may be modified invarious forms within the scope of the gist of the invention.

For example, when the golf club 3 is a right-handed golf club, theprocessing unit 21 may set the axial direction of the graph so that thearrangement pattern of the areas A1 to A9 is the same as thatillustrated in FIG. 15. When the golf club 3 is a left-handed golf club,the processing unit 21 may set the axis direction of the graph so thatthe area A1 of the push slice and the area A9 of the pull hook areexchanged with each other, the area A2 of the slice and the area A8 ofthe hook are exchanged with each other, the area A3 of the fade and thearea A7 of the draw are exchanged with each other, and the area A4 ofthe push and the area A6 of the pull are exchanged with each other inFIG. 15.

The processing unit 21 can determine whether the golf club 3 is aright-handed golf club or a left-handed golf club, for example, based onthe club specification information 242 or the like.

When the golf club 3 is either a right-handed golf club or a left-handedgolf club, the processing unit 21 preferably sets the origin of thegraph such that the area A5 of the straight is located in the middle ofthe graph.

The processing unit 21 according to the foregoing embodiment hasclassified into the 9 types of projectile lines, but may classify 2 to 8types of projectile lines or 10 or more types of projectile lines. Forexample, the projectile lines may be classified into 3 types ofprojectile lines, “hook”, “straight”, and “slice” or may be classifiedinto 3 types of projectile lines, “push”, “straight”, and “pull”. Forexample, when projectile lines are classified into 3 types, theabove-described projectile line prediction map may be divided into 3areas along one coordinate axis.

In the foregoing embodiment, the data reported to the user has beenconfigured as the combination of the incident angle θ and the relativeface angle ϕ′. However, the data may be configured as only the incidentangle θ or may be configured as only the relative face angle ϕ′.

The processing unit 21 according to the foregoing embodiment has plottedthe measurement results of the plurality of times of the user on thegraph. However, the measurement results of the plurality of times of theuser may be statistically calculated and the statistical results may bereported to the user. For example, as illustrated in FIG. 17, ahistogram of the relative face angle ϕ′ may be generated and displayedon the display unit 25. The horizontal axis of the histogram in FIG. 17is the relative face angle ϕ′ and the vertical axis of the histogram isa frequency.

The processing unit 21 according to the foregoing embodiment maygenerate and display a histogram of the incident angle θ as in thehistogram of the relative face angle ϕ′.

The processing unit 21 according to the foregoing embodiment sets, asthe movement direction vector V_(d)(t₃), the unit vector oriented in thesame direction as the vector in which the face coordinates P_(F)(t₃) attime t₃ are a starting point and the face coordinates P_(F)(t₃+Δt) attime (t₃+Δt) are an ending point . A unit vector oriented in the samedirection as a vector in which face coordinates P_(F)(t₃−Δt) at time(t₃−Δt) are a starting point and the face coordinates P_(F)(t₃) at timet₃ are an ending point may be set as the movement direction vectorV_(d)(t₃).

Alternatively, a unit vector oriented in the same direction as a vectorin which the face coordinates P_(F)(t₃−Δt) at time (t₃−Δt) are astarting point and the face coordinates P_(F)(t₃+Δt) at time (t₃+Δt) arean ending point may be set as the movement direction vector V_(d)(t₃).

Alternatively, the processing unit 21 according to the foregoingembodiment may calculate the movement direction vector V_(d)(t₃) inaccordance with, for example, the following processes (1) to (3).

(1) The trajectory Q of the face coordinates P_(F) during a given periodincluding times before and after time t₃ is calculated.

(2) A tangential line of the trajectory Q at time t₃ is calculated.

(3) A unit vector oriented in the same direction as the tangential lineis set as the movement direction vector V_(d)(t₃).

The processing unit 21 according to the foregoing embodiment hasdisplayed the measurement results as the graph, but may display themeasurement results as numerical values.

When the processing unit 21 according to the foregoing embodimentcalculates the angle formed by the movement direction vector and theface vector, the vectors have been projected to the XY plane (which isan example of the predetermined plane), but a plane to which the vectorsare projected may be another predetermined plane intersecting in thevertical direction (the Z direction). For example, the plane may be apredetermined plane including a movement direction of the head (or theface surface) of the golf club.

The processing unit 21 according to the foregoing embodiment hascalculated the angle formed by the movement direction vector and theface vector on the predetermined plane as the index indicating theposture of the face surface for which the movement direction of the facesurface is set as the criterion. However, an angle (or the magnitude ofthe angle) formed by the movement direction vector and the face vectorin a space (XYZ space) may be calculated.

When the processing unit 21 according to the foregoing embodimentcalculates the angle formed by the movement direction vector and theface vector, the vectors have been projected to the common predeterminedplane. However, the vectors may be projected to mutually differentpredetermined planes or only one of the vectors may be projected to apredetermined plane.

The processing unit 21 according to the foregoing embodiment has usedthe angle between the movement direction vector and the face vector asthe index indicating the posture of the face surface for which themovement direction of the face surface is set as the criterion. However,for example, another index such as a difference vector between themovement direction vector and the face vector may be used.

The processing unit 21 according to the foregoing embodiment has usedthe unit vector (which is an example of a predetermined vectorintersecting a ball hitting surface) oriented in the +X axis directionat time t₀ as the face vector. However, another vector fixed to the facesurface may be used as the face vector. For example, a unit vector(which is an example of a predetermined vector which lies along the ballhitting surface) oriented in the −Y axis direction at time t₀ may beused as the face vector.

Alternatively, when the posture of the face surface at time t₀ is knownfrom the club specification information 242 and the sensor-mountedposition information 244, a normal vector (which is an example of apredetermined vector intersecting the ball hitting surface) of the facesurface may be used as the face vector.

The processing unit 21 according to the foregoing embodiment hasdisplayed the measurement result as the graph, but may directly displaythe type of projectile line predicted from the measurement resultinstead of the display of the graph or in addition to the display of thegraph. In this case, for example, the processing unit 21 may display atext image indicating the predicted type of projectile line on thedisplay unit 25 or may display an image of a projectile line curveindicating the predicted type of projectile line on the display unit 25.

The processing unit 21 according to the foregoing embodiment has adoptedthe image as the report form of the measurement result. However, forexample, another report form such as a time change pattern of lightintensity, a time change pattern of a color, a change pattern of soundstrength, a change pattern of a sound frequency, or a rhythm pattern ofvibration may be adopted.

In the foregoing embodiment, some or all of the functions of theprocessing unit 21 may be mounted on the side of the sensor unit 10.Some of the functions of the sensor unit 10 may be mounted on the sideof the processing unit 21.

In the foregoing embodiment, some or all of the processes of theprocessing unit 21 may be executed by an external device (a tablet PC, anote PC, a desktop PC, a smartphone, a network server, or the like) ofthe swing analysis device 20.

In the foregoing embodiment, some or all of the acquired data may betransmitted (uploaded) to an external device such as a network server bythe swing analysis device 20. The user may browse or download theuploaded data with the swing analysis device 20 or an external device (apersonal computer, a smartphone, or the like), as necessary.

The swing analysis device 20 maybe another portable information devicesuch as a head mount display (HMD) or a smartphone.

In the foregoing embodiment, the sensor unit 10 is mounted on the gripof the golf club 3, but may be mounted on another portion of the golfclub 3.

In the foregoing embodiment, each motion of a swing of the user 2 hasbeen detected using the square root of the sum of the squares as informula (1) as the composite value of the triaxial angular velocitymeasured by the sensor unit 10. Alternatively, a sum of squares of thetriaxial angular velocities, a sum or an average value of the triaxialangular velocities, a product of the triaxial angular velocities, or thelike may be used as the composite value of the triaxial angularvelocities. Instead of the composite value of the triaxial angularvelocities, a composite value of triaxial accelerations such as a sum ora square root of squares of the triaxial accelerations, a sum or anaverage value of the triaxial acceleration, or a product of the triaxialaccelerations may be used.

In the foregoing embodiment, the acceleration sensor 12 and the angularvelocity sensor 14 are embedded to be integrated in the sensor unit 10.However, the acceleration sensor 12 and the angular velocity sensor 14may not be integrated. Alternatively, the acceleration sensor 12 and theangular velocity sensor 14 may be mounted directly on the golf club 3 orthe user 2 without being embedded in the sensor unit 10. In theforegoing embodiment, the sensor unit 10 and the swing analysis device20 are separated from each other. However, the sensor unit 10 and theswing analysis device 20 may be integrated to be mounted on the golfclub 3 or the user 2.

In the foregoing embodiment, the swing analysis system (swing analysisdevice) analyzing a gold swing has been exemplified. However, theinvention can be applied to a swing analysis system (swing analysisdevice) analyzing swings of various exercises such as tennis orbaseball.

The foregoing embodiments and modification examples are merely examples,but the invention is not limited thereto. For example, the embodimentsand the modification examples can also be appropriately combined.

The invention includes configurations (for example, configurations inwhich functions, methods, and results are the same or configurations inwhich objects and advantages are the same) which are substantially thesame as the configurations described in the embodiments. The inventionincludes configurations in which non-essential portions of theconfigurations described in the embodiments are substituted. Theinvention includes configurations in which the same operationaladvantages as the configurations described in the embodiments areobtained or configurations in which the same objects can be achieved.The invention includes configurations in which known technologies areadded to the configurations described in the embodiments.

The entire disclosure of Japanese Patent Application No. 2014-258533,filed Dec. 22, 2014 is expressly incorporated by reference herein.

What is claimed is:
 1. A motion analysis system comprising: a wirelessinertial sensor that is configured to attach to a shaft of a golf club,and that measures acceleration; and a processor that is configured towirelessly communicate with the wireless inertial sensor, and that isprogrammed to: calculate an initial position and an initial posture ofthe wireless sensor at a timing of starting a swing based on measuredacceleration data received from the wireless inertial sensor; detect,based on the received measured acceleration data, a timing of actualimpact; calculate a movement direction of a ball hitting surface of thegolf club and an impact posture of the ball hitting surface at thetiming of actual impact; calculate an incident angle of the ball hittingsurface at the timing of actual impact and a relative angle of the ballhitting surface at the timing of actual impact based on the movementdirection and the posture of the ball hitting surface at the timing ofactual impact; and cause a display to display projection-related databased on the calculated incident angle and the calculated relative angleof the ball hitting surface at the timing of actual impact.
 2. Themotion analysis system according to claim 1, wherein the processor isfurther programmed to: obtain a face vector indicating the initialposture of the ball hitting surface of the wireless inertial sensor atthe timing of starting the swing based on the measured acceleration datareceived from the wireless inertial sensor.
 3. The motion analysissystem according to claim 2, wherein the movement direction vector ofthe ball hitting surface at the timing of starting the swing isprojected on a predetermined plane intersecting the ball hitting surfacein a vertical direction.
 4. The motion analysis system according toclaim 1, wherein the processor is further programmed to: calculate amovement direction vector of the ball hitting surface at the timing ofstarting the swing based on the obtained face vector.
 5. The motionanalysis system according to claim 1, wherein the processor is furtherprogrammed to: obtain a first relationship between the movementdirection of the ball hitting surface of the golf club at the timing ofstarting the swing and the impact posture of the ball hitting surface atthe timing of the actual impact; and obtain a second relationshipbetween a posture of the ball hitting surface before starting the swingand the movement direction of the ball hitting surface at the timing ofstarting the swing based on output received from the wireless inertialsensor.
 6. The motion analysis system according to claim 5, wherein theprocessor is further programmed to: output data indicating at least oneof the first relationship and the second relationship.
 7. The motionanalysis system according to claim 6, wherein the processor is furtherprogrammed to control a display to display data indicating a combinationof the first relationship and the second relationship as atwo-dimensional graph.
 8. The motion analysis system according to claim7, wherein the processor is further programmed to control the display todisplay a type of projectile line predicted from the data indicating thecombination of the first relationship and the second relationship alongwith the two-dimensional graph.
 9. The motion analysis system accordingto claim 8, wherein the processor is further programmed to control thedisplay to display a map including an area that is divided in accordancewith the type of projectile line, and the two-dimensional graph.
 10. Themotion analysis system according to claim 9, wherein the processor isfurther programmed to control the display to display the two-dimensionalgraph to be located in the middle of the two-dimensional graph.
 11. Themotion analysis system according to claim 6, wherein the processor isfurther programmed to control the display to display a plurality ofpieces of data regarding a plurality of swings at a plurality of timeswith a two-dimensional graph and to distinguish recent data from otherdata that is not recent on the two-dimensional graph.
 12. The motionanalysis system according to claim 1, wherein output received from thewireless inertial sensor used for determining the posture of the ballhitting surface at the time of actual impact during the swing isreceived at the time of actual impact, a time before the time of actualimpact, or a time after the time of actual impact.
 13. A motion analysismethod comprising: calculating an initial position and an initialposture of a wireless inertial sensor at a timing of starting a swingbased on measured acceleration data received from the wireless inertialsensor, the wireless inertial sensor being configured to attach to ashaft of a golf club, and to measure acceleration; detecting, based onthe received measured acceleration data, a timing of actual impact;calculating a movement direction of a ball hitting surface of the golfclub and an impact posture of the ball hitting surface at the timing ofactual impact; calculating an incident angle of the ball hitting surfaceat the timing of actual impact and a relative angle of the ball hittingsurface at the timing of actual impact based on the movement directionand the posture of the ball hitting surface at the timing of actualimpact; and causing a display to display projection-related data basedon the calculated incident angle and the calculated relative angle ofthe ball hitting surface at the timing of actual impact.
 14. The motionanalysis method according to claim 13, further comprising: obtaining aface vector indicating the initial posture of the ball hitting surfaceof the wireless inertial sensor at the timing of starting the swingbased on the measured acceleration data received from the wirelessinertial sensor.
 15. The motion analysis method according to claim 14,wherein the movement direction vector of the ball hitting surface at thetiming of starting the swing is projected on a predetermined planeintersecting the ball hitting surface in a vertical direction.
 16. Themotion analysis method according to claim 13, further comprising:calculating a movement direction vector of the ball hitting surface atthe timing of starting the swing based on the obtained face vector. 17.The motion analysis method according to claim 13, wherein outputreceived from the wireless inertial sensor used for determining theposture of the ball hitting surface at the time of actual impact duringthe swing is received at the time of actual impact, a time before thetime of actual impact, or a time after the time of actual impact.
 18. Anon-transitory computer readable medium that stores motion analysisprogram instructions that, when executed by a computer, causes thecomputer to: calculate an initial position and an initial posture of thewireless sensor at a timing of starting a swing based on measuredacceleration data received from the wireless sensor: detect, based onthe received measured acceleration data, a timing of actual impact;calculate a movement direction of a ball hitting surface of the golfclub and an impact posture of the ball hitting surface at the timing ofactual impact; calculate an incident angle of the ball hitting surfaceat the timing of actual impact and a relative angle of the ball hittingsurface at the timing of actual impact based on the movement directionand the posture of the ball hitting surface at the timing of actualimpact; and cause a display to display projection-related data based onthe calculated incident angle and the calculated relative angle of theball hitting surface at the timing of actual impact.
 19. Thenon-transitory computer readable medium according to claim 18, whereinoutput received from the wireless inertial sensor used for determiningthe posture of the ball hitting surface at the time of actual impactduring the swing is received at the time of actual impact, a time beforethe time of actual impact, or a time after the time of actual impact.